Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 377
The Storm Prediction Center issued this mesoscale discussion at Apr 13, 2021, 11:43 AM CDT for 22 parishes in Louisiana; Hancock County, Harrison County, Mississippi. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 13, 2021, 11:43 AM CDT (16:43 UTC)
- Expired
- Apr 13, 2021, 1:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 24 counties
Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, Hancock County, MS, Harrison County, MS
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 4.7 hours before the alert went out and 64 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1989 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 70 m²/s²
- 0-3 km storm-relative helicity
- 88 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
815
ACUS11 KWNS 131644
SWOMCD
SPC MCD 131643
MSZ000-LAZ000-131845-
Mesoscale Discussion 0377
NWS Storm Prediction Center Norman OK
1143 AM CDT Tue Apr 13 2021
Areas affected...southern Louisiana/southern Mississippi
Concerning...Severe potential...Watch possible
Valid 131643Z - 131845Z
Probability of Watch Issuance...60 percent
SUMMARY...Along with ongoing/local hail potential, risk for locally
stronger wind gusts may increase to the point that WW issuance is
warranted in the next hour or so.
DISCUSSION...Latest radar loop shows a cluster of storms ongoing
across portions of southern Louisiana at this time, near a marine
warm front lying west-to-east across southern Louisiana. Several of
the stronger storms -- including a small segment now approaching
Tangipahoa Parish that has shown bowing tendencies over the past
half hour or so -- have remained slightly elevated, north of the
aforementioned front. However, though additional heating will be
largely mitigated by increasing/expansive cloud cover, a slow
northward advance of the higher theta-e air will contribute to some
increase in risk for gusty/possibly damaging winds with stronger
storms. Some signs of organization of convection in
Lafayette/northern Vermilion Parish may represent a portion of this
increasing wind risk. As such, WW issuance my be needed over the
next hour, for portions of southeastern Louisiana.
..Goss/Thompson.. 04/13/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LIX...LCH...
LAT...LON 30428906 30868991 30379221 29739300 29059071 28928914
29408874 30428906SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 13, 8:28 AM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Ascension, Assumption, Avoyelles, East Baton Rouge and 11 more | 2 hr |
| Apr 13, 12:06 PM CDT | Severe Thunderstorm Watch | SPC | Ascension, Assumption, Iberia, Iberville, Jefferson, Lafourche and 10 more | 6 hr |
| Apr 13, 2:44 PM CDT | Mesoscale Discussion | SPC | Iberia, Jefferson, Lafourche, Plaquemines, St. Mary, Terrebonne and 1 more | 2 hr |
| Apr 13, 3:43 PM CDT | Mesoscale Discussion | SPC | De Soto | 2 hr |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Mississippi, 2021Every mesoscale discussion in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive.